The present invention relates to magnetic random access memory (MRAM). More particularly, the invention relates to minimizing metal migration in the MRAM.
Magnetic random access memory (MRAM) utilizes magnetic fields created by the flow of electrons to sense and change the state of magnetic material. The magnetic field strengths generated by these currents must be sufficient to change the robust, stable magnetic state of the material. However, high current density introduces electron flow that pushes around metal grains to cause increased metal migration in conductors, which carry currents necessary to perform the work function on magnetic material. Hence, this requirement introduces a tradeoff between the current density capabilities of the conductors and the stiffness of the magnetic material. These contradictory requirements may force the designer to push the currents to the maximum values allowed under the metal migration constraints of the conductors.
Accordingly, based on Nickel-Cobalt-Iron (NiCoFe) magnetic material, the current required may be in the milliampere (mA) range. But the capability of the bit-line and word-line to carry this much current for sustained periods may not be feasible for this type of magnetic memory application. Although current requirements may change with the selection of alternative magnetic material and/or the modification to the magnetic structures, such selection/modification may not be sufficient to substantially eliminate metal migration concern. One conventional approach to metal migration concern has been to minimize the time that the current is flowing. However, this may not be practical in memory technologies where increased performance and density are expected.